and ben tracy has a just- elleased interview of richard nixon talking about the tape that forced him to resign 40 years ago this week. >> this was the final blow, the final nail in the coffin, although you don't need another nail if you're already in the coffin, which we were. captioning sponsored by cbs this is the "cbs evening news" with scott pelley. >> pelley: good evening. this is our western edition. the war in afghanistan may be winding down, but for u.s. forces, it can be as dangerous as ever. an american two-star general was shot dead today when an afghan soldier opened fire on a high- level delegation of officers visiting a secure military post outside kabul. major general harold greene the highest ranking officer killed in battle overseas in 44 years. david martin is working on the story at the pentagon. >> reporter: it happened at e dday at the military academy where afghans are trained to become officers. a delegation of u.s. and allied officers was mowed down by a man believed to be an afghan army soldier who opened fire with a machine gun from the window of a nearby bu